Magnetic vortex oscillator driven by d.c. spin-polarized current

• DOI: 10.1038/nphys619
• Publication Date: 2007-05-08T09:24:45Z
• Authors: V. S. Pribiag; I. N. Krivorotov; G. D. Fuchs; P. M. Braganca; O. Ozatay; J. C. Sankey; D. C. Ralph; R. A. Buhrman
• Keywords: Condensed Matter - Other Condensed Matter; 0103 physical sciences; FOS: Physical sciences; 02 engineering and technology; 0210 nano-technology; 01 natural sciences; Other Condensed Matter (cond-mat.other)

Transfer of angular momentum from a spin-polarized current to a ferromagnet provides an efficient means to control the dynamics of nanomagnets. A peculiar consequence of this spin-torque, the ability to induce persistent oscillations of a nanomagnet by applying a dc current, has previously been reported only for spatially uniform nanomagnets. Here we demonstrate that a quintessentially nonuniform magnetic structure, a magnetic vortex, isolated within a nanoscale spin valve structure, can be excited into persistent microwave-frequency oscillations by a spin-polarized dc current. Comparison to micromagnetic simulations leads to identification of the oscillations with a precession of the vortex core. The oscillations, which can be obtained in essentially zero magnetic field, exhibit linewidths that can be narrower than 300 kHz, making these highly compact spin-torque vortex oscillator devices potential candidates for microwave signal-processing applications, and a powerful new tool for fundamental studies of vortex dynamics in magnetic nanostructures.<br/>14 pages, 4 figures<br/>